Frequency of HIIT workouts?

[paydirt]

I am genetically predisposed to sprinting over long-distance running. I've just started HIIT (and in no danger of quitting) and doing sprinting on the treadmill. After two workouts, I don't feel any soreness. I don't really feel extremely nauseous after a HIIT workout. I feel a slight uneasyness that I would feel after a tough steady-state cardio workout.

So the literature about HIIT says that it should be limited to 3 workouts per week or every other day. I was wondering why? Why shouldn't I do it everyday? (the summary literature doesn't seem to say, but maybe the studies do?) Does it have to do with muscle repair or increased metabolism between workouts? If the studies don't say, what would your instincts say?

My latest workout was 13 intervals of 10mph 15sec sprints. The time between sprints is long enough so my HR gets down to 160 before each sprint (my first 3-4 intervals were 11mph).

 

[Steve]

The gist of it is HIIT in its purest form involves max exertion. Exercise modalities that call on this level of exertion tend to be taxing systemically on our bodies; meaning at the local muscular level as well as the nervous system level.

Anything that requires high neural drive for execution is considered CNS-intensive work. Over-stress the mechanics of the nervous system and you're setting yourself up for overtraining. People throw that term around quite a bit.... but true overtraining is not a good state to be in.

Throw dieting into the mix. Recovery is at a premium while dieting, meaning recoverability diminishes in the face of inadequate caloric-intake. With this being the case, you have to be very, very economical with the application of CNS-intensive training modalities.

There's a continuum, if you will, of recoverability which is dependent on genetics as well as diet. Basically, the *harder* you are dieting, the less the frequency of intensive work (i.e., HIIT, max effort lifts, etc) should be done.

This is why a consolidation of intense modalities is wise. For instance, if you're lifting weights and doing anaerobic running such as HIIT, it's best to consolidate these into intensity days. The less days per week where intense training is applied, the more days of recovery will be available.

But remember, all this is assuming a) you are doing true HIIT and b) you are dieting relatively hard.

 

[paydirt]

Cool, thanks. I'm probably doing true HIIT, though I might be pushing my peak HR too high? (it spikes to 180 or so by the end of the sprint). As far as my dieting, I should be losing 1 to 1.5 pounds per week (currently 195#)

I'd like to try and get in 6 workouts a week, so I will take your advice of combining high intensity into single days and add weight-lifting to the mix and give myself a full rest day between workout days.

If that ends up stressing my CNS too much, would the main symptom be DOMS or something else?

 

[Steve]

No, not DOMS.

DOMS measures next to nothing.

Signs of systemic overtraining would be things such as a decrease in performance, decreased desire to train, general fatigue, nagging pains, etc.

Even though you enjoy doing HIIT better than steady state cardio (which I agree with you, I'm a born sprinter with what I would believe is a dominance in ratio of fast twitch to slow twitch muscle fibers), beating your body into submission while dieting is usually not going to lead to good things.

Put it this way, when I diet down, I'll do 2 sessions of HIIT each week, usually on my leg training days as well as steady state cardio as needed whenever.